The present invention relates to the field of rodent edibles, and more particularly to rodent foods and rodenticides which are voluntarily ingested by rodents and which are intended to limit or diminish the population thereof by death, sterilization, or otherwise.
Considerable work has been conducted on the feeding and food preference habits of various rodents, particularly rats and mice. It has long been known that rodents transfer information concerning foods they have ingested, although prior investigators have not determined what mechanism is responsible for such information transfer. In Galef et al, "Transfer of Information Concerning Distant Foods: A Laboratory Investigation of the `Information-Centre` Hypothesis", Animal Behavior, 31: 748-758 (1983), "observer" rats are disclosed as preferring a diet previously eaten by a "demonstrator" conspecific with whom the observer has interacted prior to making its choice between diets. Galef et al disclose the demonstrator influence on observer diet selection is maintained even if, during the period of demonstrator-observer interaction, the demonstrator is anesthetized and a wire-mesh barrier prevents the demonstrator from physically contacting the observer. Demonstrator influence on observer diet choise is blocked by either rendering the observer anosmic or placing a transparent plexiglass barrier between demonstrator and observer during their period of interaction. Galef et al thus concluded that olfactory cues passing from the demonstrator to the observer provide observers with information concerning the demonstrators' diets and that these olfactory cues are sufficient to bias diet selection by the observers.
In Galef et al, "Transfer of Information Concerning Distant Food in Rats: A Robust Phenomenon", Animal Learning and Behavior, 12(3): 292-296 (1984), an observer rat's diet preference for the diet eaten by a demonstrator was reported for first-generation laboratory bred wild rats as well as domesticated rats; food-deprived as well as non-deprived observers; unfamiliar as well as familiar demonstrator-observer pairs; both 21 day old and adult observers; and rats selecting fluids as well as solids for ingestion. These data were reported as indicating that the social transmission of information concerning distant diets is a general and robust phenomenon, observable under a wide variety of experimental conditions.
Galef et al, "Demonstrator Influence on Observer Diet Preference: Effects of Simple Exposure in the Presence of a Demonstrator", Animal Learning and Behavior, 13: 25-30 (1985) reports that observer experience of diet-related cues in the stimulus context provided by the presence of a demonstrator was sufficient to enhance observer preference for a diet, where simple exposure to that diet was not. Galef et al report that demonstrator-induced changes in observer preference could be explained by a number of hypotheses, one of which is that the effective olfactory cue passing from the demonstrator to the observer is simply the smell of the food a demonstrator has contacted and ingested. Alternatively, Galef et al hypothesize that the demonstrator-emitted cue that is effective in altering the diet preference of an observer is a combination of the smell of demonstrator-ingested diet and some demonstrator-produced "signal". In a series of experiments intended to test these hypotheses See Galef et al., "Demonstrator Influence on Observer Diet Preference: Analyses of Critical Social Interactions and Olfactory Signals", Animal Learning & Behavior, 13: 31-38 (1985), observer rats were caused to interact with anesthetized demonstrators whose faces had been rolled in a particular diet. In subsequent simultaneous choice tests between that diet and another diet, the observer rat preferred the diet in which the demonstrator's face was rolled. In another experiment, observer rats were caused to interact with a demonstrator freshly killed by anesthetic overdose, whose face was rolled in a particular diet. In a subsequent choice between diets, including the particular diet, the observer was indifferent. In a further reported experiment, an observer rat interacted with a surrogate rate (a roll of cotton batting) one end of which was rolled in a particular diet. In a subsequent choice between that diet and another diet, the observer was indifferent. In a further experiment, either the hind quarters or the faces of demonstrators were rolled in the particular diet prior to presentation to the observers. The observers that had interacted with powdered-rear demonstrators ingested significantly less of the respective demonstrators' diets than those observers that had interacted with powdered-face demonstrators. Galef et al conclude that the demonstrator influence on observer diet preferences was not the consequence of simple exposure of observers to demonstrator-emitted cues reflecting demonstrators' diet.
In Galef et al, "Delays After Eating: Effects on Transmission of Diet Preferences and Aversions", Animal Learning and Behavior, 13: 39-43 (1985), Galef et al report that for at least four hours after ingestion, demonstrator rats emit diet related cues sufficient to alter an observers' diet preference. Diet related cues emitted by demonstrators for one to two hours after a meal were adequate conditional stimuli for aversion learning by observers. In "Utilization by Norway Rats of Multiple Messages Concerning Distant Foods", Journal of Comparative Psychology, 97: 364-371 (1983) Galef demonstrated that once an observer and demonstrator have interacted, the observer can use information acquired from a demonstrator as much as 12 hours later in selecting a diet. Accordingly, this more recent paper suggests that information concerning the diet of a demonstrator may effect an observers preference for as long as 16 hours after the time of the demonstrators initial ingestion of the food.
More recently, in a manuscript currently in press entitled "Social Identification of Toxic Diets by Norway Rats (R. norvegicus)", Journal of Comparative Psychology, (1986), Dr. Galef reports on experiments involving naive rats who interacted with two demonstrators who had recently eaten a diet unfamiliar to the observer. The observer then ate two unfamiliar diets in succession, one of which was the food its demonstrators had eaten. The observer was then subjected to toxicosis and again was offered a simultaneous choice between the two diets it had eaten prior to toxicosis induction. During the choice test, observers exhibited an aversion to that diet their respective demonstrators had not eaten. The results indicate that exposure of a rat to conspecifics that have eaten a diet can act, as does actual ingestion of a diet, to reduce the diet's subsequent associability with toxicosis.
Each of the above-identified Galef and Galef et al papers are hereby incorporated by reference as though fully set forth herein.
In addition to the information conveyed as a result of demonstrator-observer interactions, it is also known that rodents tend to prefer to eat food which has already been partially consumed by their conspecifics. This phenomenon occurs whether or not the individual has had direct contact with a demonstrator conspecific, provided the food in question has quite recently been partially consumed. See Galef and Beck, "Aversive and Attractive Marking of Toxic and Safe Foods by Norway Rats", Behavioral and Neural Biology, 43: 298-310 (1985).
Accordingly, while considerable research has been conducted and much information exists concerning rodent food preferences, the literature in this field has yet to identify whether a specific chemical or olfactory signal is generated by one rodent which is used or relied upon by another in making food preference decisions. Nor, if such signal exists, has the art identified what that signal is.
The present invention also relates to the field of volatile sulfur compounds. Volatile sulfur compounds are known to be present in human breath, and have been identified as a major source or halitosis. In other contexts, liquids or syrups smelling like rotten eggs (probably containing hydrogen sulfide) have been used as repellents for certain wildlife, particularly deer. These liquids or syrups were used in bottles having wicks placed near deer marking spots, as for example, in orchards, for the purpose of repelling deer. More recently, materials smelling like rotten eggs have been used as coyote lures in combination with traps or explosive devices intended to control coyote populations.